At last history hits pay dirt. For years it was pap for television. The nation's rulers needed scientists for guns, linguists for trade and economists for mistakes. History was for nuts and numismatists. Now up pops Charles Clarke jingling bags of gold. The home secretary has promised the prime minister that he will lock away for five years anyone who "glorifies, exalts or celebrates" a terrorist act committed in the past 20 years. He does not care if glorification was not meant. If someone, somewhere takes anything that I say or write as encouraging to terror, even if they do not act on it, I have committed a criminal act.

Nor is this all. Lest any crackpot thinks he can dance up and down any old high street praising Hitler, Mao or Uncle Joe as outside the 20-year limit, Clarke is preparing a list of earlier terrorist acts that also render their celebrants criminals. After "listed" historic buildings we have "listed" historic terrorisms. To the glorious chronicles of our island race, Clarke is to append an open-ended catalogue of listed events. They may include any acts of violence against people, property or, bizarrely, electronic systems anywhere in the world if intended to advance a political, religious or ideological cause or to influence a government.

I am told that this astonishing bill was cobbled together not by Clarke or the lord chancellor, Charles Falconer, who were both away at the time. The author was a No 10 wonk who was trying to think up "12 points" to put in Blair's holiday press conference pack on August 5. The wording recalls the remit of the old House Un-American Activities Committee in Washington. It is born of Joe McCarthy out of 1066 and All That, with a dash of the Soviet Academy of Sciences.

A sure sign of a leader losing his grip on reality is when he starts meddling with history. New Labour was born denying its past. As George Eliot said of women, happy is the one who has no history. Blair's party was not-Labour, not-Liberal, not-Tory, just "we". Hence the significance of Clarke's partial cut-off date in the mid-80s. That was the time when Blairism first oozed like ectoplasm from the guts of Orgreave and Wapping.

Terrorism as defined in law more or less covers the story of the human race. Half of Churchill's History of the English-Speaking Peoples must qualify as a listed event. The Crown Prosecution Service must be staffed with experts in William the Conqueror, the Black Prince, the New Model Army, the Gordon rioters, the Tolpuddle Martyrs. Spin doctors must cut their teeth on Alexander the Great, Vlad the Impaler, Innocent III and the Counter-Reformation in Latin America. They must burn midnight oil over the Albigensian crusade. Blair will be heard screaming in his attic: "Beware the Da Vinci Code."

This is government by trivia and whim. Already we are told that Clarke's listed events will not include anything Irish. Why? King William's campaign is life and breath to loyalist militants, as is the 1916 Easter Rising to Blair's pet insurrectionists, the IRA. Why should these groups be excused the law? Soon anyone who visits terror on the British people will negotiate a "listed events exclusion clause" as part of their final settlement.

Even without the cliche that one man's listed event is another's act of heroism, this is a can of worms. Bomber Harris's flattening of German cities in the second world war was specifically described by Churchill as "simply for the sake of increasing terror". The bombing of Hiroshima was, to put it mildly, a politically motivated assault on people and property. Last month it was not glorified, but it was certainly celebrated.

Are Hiroshima or Dresden to be listed events? If not, how can the no less terrorist blitz be listed? Conrad was in this sense right: "The terrorist and the policeman both come from the same basket." I have no faith in Clarke's Stalinist historians. If Whitehall bureaucrats are so otherworldly as to find village ponds, conker trees and rare steaks awash in human hazard, there is no telling what they will find in the bloodstained pages of history. They need only to find a dodgy event and someone to praise it and they will pounce. The issue is not mens rea or intention to glorify. To convict, there need only be someone who confesses to being "encouraged" by the glorification. It is a stooge's charter.

This extension of censorship renders any apologist for any liberation struggle vulnerable to prosecution. I find it astounding that people such as Falconer, Clarke and the rest of the cabinet can sit round a cabinet table and pass a measure worthy of Joseph Goebbels.

Ministers may yet be hoist with their own petard. I might draw a moral distinction between Blair's crusade against certain Muslim states and, say, publicity for al-Qaida violence against me. I might feel that my war is in a good cause and theirs an evil one.

The courts are not free to make that distinction. Any act with terrorist connotations puts not just its perpetrator but any contributory publicity at risk. Operation Shock and Awe against Baghdad in March 2003, in which Britain participated, was intended to terrify the civilian population to the political end of toppling Saddam. The name boasted it.

Government lawyers may argue that states cannot be terrorists, yet those same lawyers apply the phrase "state terrorism" to others. Besides, the bill offers no defence of "good cause". The Crown Prosecution Service must surely apply the law impartially.

The government's defenders will argue of terror-bombing from the air that there are distinctions in targeting and collateral damage. But any self-respecting terrorist can find similar excuses for horror. At very least Downing Street is vulnerable to hypocrisy. Its crude attempt to stoke war fever in the winter of 2002/3 with briefings of "new smallpox/ricin/anthrax threat to London" was no less political. It was meant to frighten the public into supporting the rush to war. The effect was to disseminate the same fear as did the supposed terrorists. Bluntly, the government was doing the terrorists' job for them. I cannot see how this puts ministers above their own law.

Downing Street is not alone in playing this tune. This week Brussels joined in the New Orwellianism. In a document called Terrorist Recruitment: Addressing the Factors Contributing to Violent Radicalisation, the European Commission warns the media not to take a "reductionist and conspiratorial world view where inequity and oppression are dominant". It singles out journalism as offering a "specific risk" in the fight against terrorism - the risk of "oversimplification". Journalists should apparently watch themselves. The edict is the work of the commission's vice-president and ally of Silvio Berlusconi, Franco Frattini. Berlusconi is no friend of the press.

What is going on here? Blair, Clarke and Falconer are consorting with strange company. They should remember Montaigne's warning to history: "To make judgments about great and high things, a soul of the same stature is needed." Otherwise, said the great man, we drag history down to the level of our own vices. Just so.